This exploratory R21 project will test the hypotheses that apparent deficits in symbolic capacity shown by children with neurodevelopmental disabilities be may 1) explainable as deviant, typically unmeasured stimulus control processes rather than capacity limitations per se and 2) correctable by better measurement and procedural management of such processes. Our primary study population will be nonverbal children with autism, a disorder characterized by deficits in joint attention, symbolic functioning, and restriction in behavioral repertoires. Symbolic relations will be defined operationally in two ways. The first is in terms of contingency-defined functional equivalence relations involving classification according to concurrent shifts in stimulus functions. The second is in terms of mathematically derived stimulus equivalence relations. Our primary objective is to analyze inter- and intra-participant variability in the acquisition of equivalence relations, previously demonstrated in studies of children with autism and in nonhuman analogue studies. We will compare procedures used in past studies with procedures designed specifically to minimize or eliminate stimulus control relations that we posit are incompatible with acquisition of equivalence relations. The latter will control procedurally stimulus relations that have been left free to vary in past studies of functional and stimulus equivalence acquisition, including degree of learning set formation prior to functional equivalence tests, and the development of both positive and negative instances of relational control. Our studies of children with autism will be supplemented by parallel collaborative studies with colleagues who are pursuing similar questions with capuchin monkeys. Taken together, our studies are intended to advance understanding of the symbolic potential of nonverbal children with autism and to develop procedural solutions to challenges in building on that potential in functional communication training. PUBLIC HEALTH RELEVANCE: This project will investigate the development of symbolic behavior in children with autism spectrum disorders and little or no functional language. We hope that our research will lead to teaching interventions in the area of functional communication and to methods that will make positive outcomes of behavior therapy more robust and reliable.